LS Engine Swap In A Muscle Car - How It Works

LS swaps are smoking hot and here’s how to fit one inside your muscle car

Hot rodders have known about the power of the Gen III/IV for quite some time, and it’s not news to anyone that they’re being dropped into just about everything. They’re so popular, in fact, that many engine shops now report that conventional builds are on the decline. That sounds downright wacky at first, but think about it for a short while and it makes perfect sense. Not only can you make 650-plus streetable horsepower with an LS small-block these days, but you can build them as large as 500 ci. Throw in the weight and handling benefits of an all-aluminum platform, especially in Pro Touring projects, and the swap appeal of these motors becomes quite obvious.

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Whether plans call for a 9,000-rpm screamer or a stock salvage yard score, swapping an LS motor into classic Bow Tie muscle is easier than ever. Several aftermarket manufacturers offer engine mounts, headers, oil pans, and transmission crossmembers that make an LS retrofit a strictly bolt-on affair. Even so, there are lots of potential hiccups that can easily be avoided with a bit of research. Gen III/IV small-blocks rolled off the assembly line with a number of different front accessory drive, intake manifold, oil pan, and throttle-body designs, all of which can affect how smoothly your swap progresses. To get to the bottom of it all, we had a chat with Marc Lewis of Hedman Hedders, Liz Miles of Hooker Headers, and Mark Campbell of Street and Performance. Here’s their advice for a fruitful LS swap.

Headers

Marc Lewis: Swapping an LS motor into a muscle car used to require very expensive custom headers, but that’s not the case anymore. The application list of Muscle Rods LS swap products manufactured by Hedman Husler Hedders is a virtual alphabet soup of iconic GM cars and trucks. Unlike some products that can be produced as a one-size-fits-all product, headers cannot. Header primary tubes are built using rigid, immovable tubes. When a manufacturer designs a set of headers, they must determine the most effective path to use for the tube routing, so they do not interfere with steering or suspension components, auxiliary engine/vehicle components, crossmembers, or chassis components. Change any of the variables in the engine compartment, and you risk hitting any number of items. This can bring your installation to a screeching halt. Although many installers like to use the gentle persuasion of a hammer to make a set of headers fit, this is not what most manufacturers intended for you to do. Not only will banging on your tubes negatively affect the performance you expect to gain from the headers, a beaten set of headers just doesn’t look very good under the hood.

For the reasons mentioned above, Hedman Husler has invested countless hours developing its LS swap headers and motor mounts to ensure that they fit right in without any need for massaging. The R&D team at Husler’s Georgia plant did this by bringing in specimen vehicles that matched the most frequently used setups. While on the racks, the Husler designers develop mid-length and long-tube headers in a variety of diameters, as well as companion motor mounts and transmission crossmembers. The Hedman Husler guys basically did all the trial-and-error work before the parts ever hit the market. These headers are currently in production for Chevy Tri-Five and X-frame cars, as well as A-, B-, F-, G- and X-bodies. We also offer a range of headers for ’67-98 two-wheel-drive GM half-ton trucks and SUVs.

Each series of Muscle Rods headers are available as mid-length headers with a ball-and-socket–style collector, or as full-length headers with a race-style collector. For those wanting to utilize headers that provide maximum power potential, full-length headers with stepped primary tubes are also available. Tube diameters range from 1.625- all the way up to 1.875x2-inch stepped tubes. Regardless of the tube style or diameter, the smooth, mandrel-bent Muscle Rods tubes provide performance that is far superior to cast LS manifolds or generic LS headers. The Husler R&D gurus went so far as to tune the primary tube lengths to work with the LS engine’s timing curve. This added feature optimizes exhaust scavenging for maximum power potential. In fact, mid-length Muscle Rods models can add as much as 20-25 hp at the rear wheels, and full-length models can add as much as 45 hp. All Muscle Rods LS Swap headers are offered in a variety of finishes. LS guys can choose from raw mild steel headers that they can finish however they want, Hedman’s HTC silver ceramic-metallic coating, or Husler’s new Black Maxx ceramic-metallic finish.

Liz Miles: Hooker offers headers for several LS swap applications, and is constantly engineering new ones to add to this list. Currently, we have Super Competition LS swap headers for ’55-57 Chevys, ’67-69 Camaros, and ’68-72 Chevelles. Coming soon are swap headers for second-generation Camaros as well. These headers feature 1.75-inch primaries, thick 5/16-inch flanges, 3-inch collectors, and 18-gauge steel tubing. To suit a wide variety of applications, Hooker headers are available in our traditional metallic ceramic coating, and our Darksides ceramic coatings. While our traditional metallic ceramic coatings are good for up to 1,300 degrees F, the Darksides’ coating can withstand temperatures up to 1,700 degrees. This makes it an excellent choice for forced-induction and nitrous applications. Additionally, soon to be released are our new cast-iron exhaust manifolds for use with the E-rod crate engine, or any other application where space, simplicity, or a nostalgic look is desired.”

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Crossmembers

Mark Campbell: After retrofitting an LS motor into the engine compartment, the next step is figuring out how to support the transmission. F- and X-bodies, Tri-Fives, and ’58-64 fullsize Chevys typically require an aftermarket crossmember in order to use a late-model GM trans. Fortunately, they are available turnkey from a number of manufacturers, including Street and Performance. On the other hand, Chevelles and late-model Caprices can use a stock crossmember. All you have to do is slide the crossmember back on the framerails, and lower or raise it to get the driveshaft angle correct. We usually recommend a driveshaft angle of -0.5 to 2 degrees. Otherwise, you’ll have driveshaft problems and wear out the U-joints.

Engine Mounts

Liz Miles: Hooker’s engine mount plates are built to be a simple, strong, and aesthetically pleasing way to easily mount an LS small-block in a muscle car. The Hooker engine swap plate bolts to the LS motor, and a standard small-block Chevy engine mount bolts to our plate. This approach eliminates much of the fabrication work required with such swaps. Built from 3/8-inch hot rolled steel, they feature counter-sunk machine screws and a durable zinc coating. Hooker’s LS engine mount plates come in a large assortment of configurations to cover a wide range of applications. The plates can position the motor in the stock location, but we also offer plates that relocate the motor 0.5, 1.25, and 3 inches forward. We even cover G-bodies with our clamshell-style mounts. LS cylinder heads extend all the way to the bellhousing mounting surface while Gen I engines have about an inch of space. This needs to be considered when selecting the plates.

Oil Pans

Mark Campbell: As with any engine swap, oil pan clearance can be an issue when retrofitting LS motors into muscle cars. For cars that require a rear sump, the factory fourth-gen F-body pan is a popular choice. For cars that require a front sump, the ’04-06 GTO pans are the way to go. The nice thing about the F-body pan is that it will fit inside a ’58-64 fullsize Chevy without any modifications. The pan will also fit Tri-Fives, Chevelles, and Camaros, but this requires removing about 2 inches from the front edge of the sump in order to clear the draglink. F-body pans can also be used on G-bodies, as long as the crossmember is notched. The factory LH8 pan works in cars that have lots of ground clearance, but it probably won’t work in a lowered muscle car. When modifying a stock pan, the cuts must be made as cleanly as possible to avoid leaks when it’s TIG welded back up. We offer this service for $243, but with these pans becoming harder to find, it might be worth it to buy an aftermarket pan that already has the necessary clearance. Street and Performance is currently developing oil pans for LS swap applications for A-, F-, and G-bodies, and X-frame cars.

Liz Miles: With LS swaps becoming more and more popular, these engines are finding their way between the fenders of more early cars than ever. Unfortunately, the factory LS passenger car pan has a tapered shape that doesn’t always clear the crossmember. Likewise, the sump of the stock truck pan hangs too low. To offer hot rodders a superior alternative, the Holley LS Retrofit Oil Pan emulates the traditional rear-sump arrangement, but we designed it for maximum ground and chassis clearance. Since it’s cast aluminum, it retains the strength and superior sealing surface of the factory pan. The six-quart capacity comes with the correct pickup and baffle to fully take advantage of the new pan’s shape. It also retains the oil filter and cooler port locations and uses the factory seals.

Front Accessories

Mark Campbell: The three most commonly used front accessory drive systems in LS swap applications are off of factory fourth-gen Camaros, C5 Corvettes, and Vortec trucks. The factory A/C compressor is quite bulky, and mounts on the lower passenger side. This usually creates interference with the K-member or control arms. On the driver side of the motor, the power steering pump and alternator can cause clearance issues. Fortunately, none of these obstacles are difficult to overcome. The F-body and Corvette accessory drives will fit into most older Chevys without a problem. The Corvette drive system works well on Tri-Fives as well as C2, C3, and C4 Corvettes. When it’s used in Tri-Fives, the motor needs to be moved up about 3/4 inch to clear the draglink, or the car can be converted to a rack-and-pinion setup. The F-body accessory drive fits inside Novas, first-gen Camaros, and G-bodies very well. The LS1 GTO accessory drive is another option, but since it has a big alternator, swapping in a smaller unit is often required. Since the alternator on the Vortec truck accessory drive sits so high, it will only fit in cars with lots of hood clearance like ’58-64 X-frame cars.

That said, small modifications can go a long way. For example, if the A/C compressor hits the K-member, an easy fix is notching the crossmember or running a smaller compressor.

Computers

Liz Miles: The Holley Dominator EFI system was built with the LS-series engine in mind. It uses all of the same inputs and outputs as a factory LS engine so it can easily be adapted to our EFI system. The software allows for nearly infinite adjustment in an extremely user-friendly format. It controls the LS engine’s injectors, ignition, and electronic automatic transmission. It can also read and tune GM’s drive-by-wire throttle body for exact control. Holley’s tuning software allows you to be as specific as you like while giving you set-it-and-forget-it ease with its self-learning programming. We carry LS engine wiring harnesses, perfect for a swap vehicle where you’re starting from scratch. If you don’t need drive-by-wire or transmission control, we also offer our HP EFI units with LS harnesses.

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Trans Tunnel Clearance

Mark Campbell: Late-model transmissions like the Tremec T56 and GM 4L60E will fit most Chevy muscle cars without a problem. Rumor has it that you have to cut up the trans tunnel, but that simply isn’t true. For instance, trans tunnel clearance is very tight on a Chevelle, but you can still fit a T56 without any cutting. The reverse lockout solenoid is what usually causes clearance problems in these cars. When it comes to fitting a trans inside the tunnel, you just have to use the right motor mounts and the correct driveshaft angle to get everything positioned properly.

Swap Bundles

Marc Lewis: All of Hedman’s Muscle Rods headers are built in conjunction with vehicle- and transmission-specific motor mounts and transmission crossmembers. When choosing these mounts for use with LS swap headers, it is important to choose the conversion kit that is specific not only to your vehicle, but the transmission you plan on using as well. Regardless of the application, our R&D team made sure that all mounts and headers allow the engine and transmission to be set with the recommended 3- to 5-degree pinion angle. In addition to the headers themselves, Hedman’s LS conversion kits come complete with a full set of engine mounts that are manufactured using 1/4-inch cold-rolled steel plate, polyurethane bushings, and Grade 8–hardened mounting hardware. Also included is a complete transmission crossmember that features thick-wall construction, a polyurethane transmission mount, and hardened Grade 8 hardware. To protect the components from the elements, and to make them look sharp, all mounts and crossmember components are given a hearty, silver powdercoated finish. Muscle Rods LS Conversion kits are very application specific. For example, four conversion kits are available for ’68-72 A-bodies, depending on whether your vehicle is a coupe or convertible, and whether you are using a manual or automatic transmission.

Clutch and Shifter

Mark Campbell: With most LS swaps where a T56 transmission is used, the shifter location is right where you want it. Street and Performance offers relocation kits that can move the shifter 2 to 4 inches forward. However, the only instances where they are necessary are when you’re trying to get the shifter to line up into a factory center console. Without a console, you rarely have to move the shifter. As for the clutch linkage, for the sake of simplicity we recommend using the stock hydraulics and pedal assembly. That way, it’s a completely bolt-in affair, and all you have to do is hook up the hydraulics to the stock pedal in the new car.

LS Fest

Liz Miles: Recognizing the popularity of LS swaps, we wanted to give these enthusiasts a place to meet and share what they have done with their cars. As a result, we created the Holley LS Fest, which is a three-day-long event held in September at Beech Bend Raceway Park in Bowling Green, Kentucky. The event includes drag racing, an autocross, a speed-stop challenge, a car show, a dyno challenge, a drift challenge, and a cruise. We know the LS engine is hot for many reasons, and we wanted to show consumers that Holley is serious about the LS market. The more we expose people to the possibilities of this incredible engine, the more encouraged we all become to build them with more power, more efficiency, better looks, and uniqueness. We also wanted to create an event that was packed with action. Obviously the LS engine is being swapped into a lot of vehicles, so we wanted to show it how it’s done in real time with the Engine Swap Challenge. In this event, two teams square off to see how quickly they can swap an LS engine into their car and get it running. The first team to fire it up wins an LS crate motor.

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Throttle-Body Hookup

Mark Campbell: LS-series small-blocks came from the factory with both cable and electronically actuated throttle bodies. Hooking up a conventional cable throttle-body is easy enough and doesn’t require much of an explanation. Likewise, when you’re shopping for a motor to swap into your car, don’t be put off by an electronic throttle body. All you need to get it to work in a retrofit application is the gas pedal out of the donor car, and the throttle actuator control (TAC) module. Just hook these items up, and an electronic throttle body will work perfectly in a swap application. CHP